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Abstract:

The invention is a modelling plate (6; 6'; 6'') for a stereolithography
machine (1) suited to produce three-dimensional objects (A) through
superimposition of a plurality of layers (E) with predefined thickness of
a liquid substance (3) that solidifies when subjected to a selective
stimulation (4). The plate (6; 6'; 6'') comprises a work surface (7) that
supports the object (A) and grooves (8) made in the work surface (7)
along a development trajectory (X).

Claims:

1) Modelling plate (6; 6'; 6'') for a stereolithography machine (1)
suited to produce three-dimensional objects (A) through superimposition
of a plurality of layers (E) with predefined thickness of a liquid
substance (3) suited to solidify when subjected to a selective
stimulation (4), said plate (6; 6'; 6'') comprising a work surface (7)
suited to support said object (A), characterized in that it comprises at
least one groove (8) made in said work surface (7) along a development
trajectory (X).

2) Plate (6; 6'; 6'') according to claim 1), characterized in that the
depth (9) of said groove (8) exceeds the predefined thickness of said
layers (E).

3) Plate (6; 6'; 6'') according to claim 1) or 2), characterized in that
said groove (8) extends to the perimeter edge of said work surface (7) so
as to have at least one open end at the level of the lateral surface of
said plate (6; 6'; 6'').

4) Plate (6; 6'; 6'') according to claim 3), characterized in that said
groove (8) has both ends open at the level of said lateral surface of
said plate (6; 6'; 6'').

5) Plate (6; 6'; 6'') according to any of the preceding claims,
characterized in that said groove (8) has a uniform cross section (11,
11', 11'') along said development trajectory (X).

6) Plate (6') according to claim 5), characterized in that said cross
section (11') has at least one area (12) whose width exceeds the width
(10) of said cross section (11') at the level of said work surface (7).

7) Plate (6'') according to claim 5) or 6), characterized in that the
profile of said cross section (11'') has a recess (13) on at least one of
the side edges of said cross section (11'').

8) Plate (6, 6', 6'') according to any of the preceding claims,
characterized in that it comprises a plurality of said grooves (8)
parallel to each other.

9) Stereolithography machine (1) for the production of three-dimensional
objects, comprising: a tank (2) suited to contain a liquid substance (3)
that solidifies when it is subjected to a selective stimulation (4);
emission means (5) suited to generate said selective stimulation (4) and
to convey it towards said tank (2), characterized in that it comprises a
modelling plate (6; 6'; 6'') according to any of the claims from 1) to
8).

10) Machine (1) according to claim 9), characterized in that said plate
(6; 6; 6'') is arranged with said work surface (7) facing the bottom (2a)
of said tank (2).

11) Machine (1) according to claim 9) or 10), characterized in that it
comprises a tool (14) for cleaning said modelling plate (6; 6'; 6''),
comprising a supporting body (15) from which at least one elongated
element (16) develops, configured so that it can slide inside a
corresponding groove (8) of said plate (6; 6'; 6'').

12) Machine (1) according to claim 11), characterized in that said tool
(14) comprises a supporting body (15) from which a plurality of elongated
elements (16) develop, each one of which is configured so that it can
slide inside a corresponding groove (8) of said plate (6; 6'; 6''), said
elongated elements (16) being mutually parallel and arranged according to
a reference plane (Y) at mutual distances that are the same as the mutual
distances between the corresponding grooves (8).

13) Machine (1) according to claim 11) or 12), characterized in that the
width (17) of each one of said elongated elements (16) with respect to a
direction parallel to said reference plane (Y) is substantially equal to
the width (10) of the corresponding groove (8) of said plate (6; 6';
6'').

14) Machine (1) according to any of the claims from 11) to 13),
characterized in that the thickness (18) of each one of said elongated
elements (16) in a direction orthogonal to said reference plane (Y) does
not exceed the depth (9) of the corresponding groove (8).

15) Machine (1) according to any of the claims from 11) to 14),
characterized in that said elongated elements (16) have rounded ends
(16a).

16) Machine (1) according to any of the claims from 11) to 15),
characterized in that said elongated elements (16) are flexible.

17) Machine (1) according to any of the claims from 11) to 16),
characterized in that the hardness of said elongated elements (16) is
lower than the hardness of said plate (6; 6'; 6'').

Description:

[0001] The present invention concerns a modelling plate for a
stereolithography machine, as well as a stereolithography machine
comprising said plate.

[0002] The present invention also concerns a tool for cleaning the above
mentioned modelling plate.

[0003] As is known, the stereolithography technique makes it possible to
produce three-dimensional objects by superimposing a succession of layers
obtained by means of a liquid resin that solidifies when subjected to a
predefined stimulation.

[0004] Each layer of the object is obtained by selectively stimulating the
resin so as to solidify it in the points that make up a corresponding
section of the object to be is produced.

[0005] As is known, a stereolithography machine generally comprises a tank
suited to contain the liquid resin, a device suited to stimulate a liquid
resin layer having a predefined thickness and a moving modelling plate
that supports the three-dimensional object during its formation.

[0006] To create the first layer of the object, the surface of the plate
is brought to the level of the above mentioned liquid layer to be
stimulated, so that the first layer of the object is formed against the
plate and adheres to it.

[0007] To create each successive layer, the plate moves the object away
from the previous position, so as to allow the resin to restore the
liquid layer that will serve to form the successive layer.

[0008] Then the plate moves the object back to such a position that the
last layer is against the liquid resin layer, so that the latter
solidifies while adhering to the previous layer.

[0009] The stereolithography machines of known type pose the drawback that
it is not easy to remove the finished object from the modelling plate.

[0010] In particular, since the object adheres to the plate and is very
fragile, it must be detached using a sharp metal blade that is slided
over the plate to separate the object from the surface of the plate
itself.

[0011] This operation involves the risk of deforming or breaking the
object and therefore it must be carried out manually and with great care,
with the double drawback of increasing labour costs and the risk of
rejects.

[0012] The blade poses another drawback lying in that some surface
particles are removed from the plate.

[0013] Besides damaging the plate, this causes another drawback,
represented by the fact that the above mentioned particles contaminate
the residual liquid resin present in the tank, thus affecting the
soundness of the objects that are produced successively.

[0014] Further drawbacks are posed by the stereolithography machines in
which the stimulation device is positioned under the tank, which is
provided with a bottom that is transparent to stimulation.

[0015] In this variant, the stimulation device is configured so as to
solidify the resin layer adjacent to the bottom of the tank itself, so
that the object is formed under the modelling plate and on creation of
each successive layer the plate is progressively lifted from the bottom
of the tank.

[0016] The vertical movements of the plate cause the resin to flow from
the centre of the plate towards its sides and vice versa, depending on
the direction of movement.

[0017] Due to the viscosity of the resin and its consequent difficulty in
flowing, the movement of the plate exerts a certain pressure on the
bottom of the tank, which increases in proportion to the viscosity of the
resin, the plate movement speed and the proximity of the plate to the
bottom of the tank.

[0018] In particular, during the formation of the first layers, the
modelling plate is arranged at a distance from the bottom of the tank in
the order of a few hundredths of a millimetre.

[0019] Therefore, during the formation of the first layers, the pressures
determined by the movements of the plate are so high that it is necessary
to limit the plate speed, with the inconvenience of considerably
increasing the processing costs. The problem described above is addressed
in the Italian patent application VI2008A000311, in the name of the same
applicant who filed the present application.

[0020] This document discloses a stereolithography machine comprising a
plate provided with through holes that, allowing the resin to flow from
one face of the plate to the other, prevent the resin from flowing
towards the sides of the plate. Therefore, advantageously, the presence
of the holes reduces the amount of pressure exerted on the bottom of the
tank and makes it possible to increase the plate movement speed even
during the formation of the first layers.

[0021] Furthermore, the holes prevent the plate from adhering to the
bottom of the tank, producing the so-called "sucker effect" described in
detail in the above mentioned document of the known art.

[0022] However, the holed plate poses the same drawbacks described above
with reference to the removal of the object and to the cleaning of the
plate, as well as adding new drawbacks.

[0023] It is known, in fact, that in order to make the layers adhere to
the surface of the plate it is necessary to stimulate a layer of resin
slightly thicker than is strictly required.

[0024] Consequently, when a holed plate is used, part of the resin
belonging to the first layers of the object solidifies inside the holes
and remains stuck therein, thus hindering the successive removal of the
plate at the end of the processing cycle.

[0025] In particular, if the object is removed by means of the above
mentioned sharp metal blade, there is the inconvenience that the portions
of resin that solidified in the holes are separated from the rest of the
object and remain stuck in the holes.

[0026] Therefore, after removing the object, a further operation is
necessary to remove the resin that is stuck in the holes.

[0027] Differently from the variant embodiment described above, a further
variant embodiment of a stereolithography machine has the stimulation
device arranged over the tank and configured so as to solidify the
surface layer of the resin.

[0028] In this embodiment, the object is formed over the plate, which is
progressively lowered as the construction of the object proceeds.

[0029] Even if this variant embodiment does not pose the drawbacks related
to the pressure exerted on the bottom of the tank, it nevertheless poses
the drawbacks related to the removal of the object from the plate and to
the cleaning of the latter, described with reference to the previous
variant embodiment.

[0030] The present invention intends to overcome all the drawbacks of the
known art as outlined above.

[0031] In particular, it is a first object of the invention to provide a
modelling plate for stereolithography machines that allows the finished
object to be removed more comfortably than allowed by the plates of known
type.

[0032] It is a further object of the invention to provide a plate that is
easy to clean.

[0033] It is also the object of the invention to provide a plate that,
when used on a stereolithography machine provided with a stimulation
device arranged under the tank, facilitates the flow of the resin from
the centre of the plate towards its sides, and vice versa, compared to
the plates of known type.

[0034] The objects described above are achieved by a modelling plate for a
stereolithography machine according to claim 1 and by a stereolithography
machine according to claim 9.

[0035] Further characteristics and details of the invention are described
in the corresponding dependent claims.

[0036] Advantageously, making it easier to remove the object from the
plate means reducing the need for labour and the number of rejects.

[0037] Furthermore, making it easier to clean the plate means reducing the
risk of contaminating the resin and thus also means offering the
corresponding advantages.

[0038] Still advantageously, the easier flow of the resin allows plate
movement speeds to be adopted that are analogous to those achievable with
holed plates of known type.

[0039] Therefore, it is possible to reduce the processing time of a single
object and thus reduce its cost.

[0040] The said objects and advantages, together with others which will be
highlighted below, are illustrated in the description of preferred
embodiments of the invention which are provided by way of non-limiting
examples with reference to the attached drawings, wherein:

[0041] FIG. 1 shows an axonometric view of the stereolithography machine
that is the subject of the invention;

[0042] FIG. 2 shows a side section view of the machine shown in FIG. 1;

[0043] FIG. 2a shows an enlarged detail of FIG. 2;

[0044]FIG. 3 shows an axonometric view of the modelling plate that is the
subject of the invention;

[0045] FIG. 4 shows a side section view of a detail of the plate shown in
FIG. 3;

[0046] FIGS. 4a and 4b show in detail a side section view of several
variant embodiments of the plate shown in FIG. 4;

[0047]FIG. 5 shows an axonometric view of a tool for cleaning the plate
of the invention;

[0049] FIG. 7 illustrates the use of the tool of FIG. 5 with the plate of
FIG. 3;

[0050] FIG. 8 shows a side section view of a detail of FIG. 7.

[0051] As shown in FIG. 1, the stereolithography machine 1 of the
invention comprises a tank 2 suited to contain a liquid substance 3
suited to solidify when subjected to a selective stimulation 4, shown in
FIG. 2.

[0052] The above mentioned selective stimulation 4 is generated through
emission means 5 that convey it towards the tank 2.

[0053] Preferably but not necessarily the liquid substance 3 is a
light-sensitive resin and the emission means 5 comprise a laser emitter
associated with scanner means 5a of any known type suited to direct the
laser beam on the points of the layer of resin 3 to be solidified.

[0054] Obviously, variant embodiments of the invention may include other
known types of emission means 5, provided that they can solidify the
liquid substance 3.

[0055] The machine 1 also comprises a modelling plate 6, provided with a
work surface 7 facing said emission means 5 and suited to support a
three-dimensional object A being formed.

[0056] The machine 1 described above makes it possible to produce the
three-dimensional object A by superimposing a plurality of layers E of
said solidified resin 3 having a predefined thickness.

[0057] In particular, the first layers adhere to the work surface 7 of the
plate 6, while the successive layers adhere to the previous ones.

[0058] Preferably but not necessarily the machine 1 is configured so as to
form the object A under the modelling plate 6, as shown in FIGS. 1 and 2.

[0059] In particular, the emission means 5 are arranged under the tank 2
that has a bottom 2a that is transparent to stimulation 4.

[0060] Obviously, in this case, the plate 6 is arranged with the work
surface 7 facing the bottom 2a of the tank 2.

[0061] According to a variant embodiment of the stereolithography machine
of the invention, not shown herein, the emission means 5 are arranged
over the tank 2.

[0062] In this second variant embodiment, the modelling plate 6 is
arranged with the work surface 7 facing upwards and the three-dimensional
object A is formed over the plate.

[0063] The plate 6 comprises a plurality of grooves 8 made in the work
surface 7 along corresponding development trajectories parallel to one
another and preferably rectilinear, as shown in FIG. 3.

[0064] During the formation of the first layers E of the object A adjacent
to the work surface 7 of the plate 6, the resin 3' located in the grooves
8 is not reached by the stimulation 4 and, therefore, remains liquid,
thus defining a corresponding number of channels interposed between the
solidified object A and the plate 6, as shown in FIG. 2a.

[0065] At the end of the processing cycle, a corresponding elongated
element 16 belonging to a cleaning tool 14, shown in FIG. 5, can be
inserted and slided into each one of the above mentioned channels.

[0066] The elongated element 16 can exert a thrusting action on the
three-dimensional object A in order to detach it from the work surface 7,
as shown in FIG. 8.

[0067] Therefore, the above mentioned grooves 8 make it easier to detach
the finished object A from the work surface 7, thus achieving one of the
objects of the invention.

[0068] Advantageously, the above mentioned thrusting action poses fewer
risks of damaging the object A than the known techniques, according to
which the object A is removed using a sharp, tool.

[0069] Furthermore, advantageously, the tool A is not provided with a
cutting edge and therefore cannot damage the plate 6.

[0070] Furthermore, as the object A is removed completely, it does not
leave solid residues inside the grooves 8, thus achieving the further
object to facilitate the cleaning of the plate 6.

[0071] The grooves 8 preferably extend to the perimeter edge of the work
surface 7, opening up at the level of the lateral surface of the
modelling plate 6, as clearly visible in FIG. 3.

[0072] It is clear that the above mentioned open end allows the resin 3 to
flow from the grooves 8 towards the lateral area of the plate 6, and vice
versa, during the vertical movement of the plate 6 itself.

[0073] Preferably, both ends of the grooves 8 are open at the level of the
lateral surface of the plate 6, advantageously allowing the resin 3 to
flow in both directions.

[0074] Therefore, if the plate 6 is arranged with the work surface 7
facing the bottom 2a of the tank 2, the resin 3 can flow along the
grooves 8 from the centre of the plate 6 towards its sides, and vice
versa.

[0075] Therefore, the invention achieves the object to facilitate the flow
of the resin 3, especially when the plate 6 is arranged very near the
bottom 2a of the tank 2.

[0076] Advantageously, the facilitated flow of the resin 3 makes it
possible to reduce the pressure exerted on the bottom 2a of the tank 2
during the vertical movement of the plate 6.

[0077] Therefore, advantageously, it is possible to select movement speeds
of the plate 6 that are equivalent to those possible, for example, with
holed plates of known type, and in any case exceed those allowed by other
known types of plate.

[0078] The grooves 8 preferably have depths 9 exceeding the thickness of
the is layers E that make up the three-dimensional object A, for example
in the order of tenths of a millimetre or more.

[0079] Advantageously, this makes it possible to prevent the first layers
of the object A from clogging the grooves 8, if solidification occurs
partly inside them due to processing needs or mispositioning of the plate
6.

[0080] The first case is the most common and derives from the fact that,
to ensure the adhesion of the first layers E to the work surface 7 of the
plate 6, a stimulation 4 is employed whose intensity is higher than the
intensity strictly necessary to solidify the layer having predefined
thickness.

[0081] The higher intensity of the stimulation causes a partial
solidification of the resin 3' arranged inside the grooves 8, as shown in
FIG. 2a.

[0082] The number of grooves 8, their width and their mutual distances on
the plate 6 are parameters that can be selected by the manufacturer based
on the operating characteristics of the machine 1 on which the plate 6
must be used.

[0083] In general, a more viscous resin 3 will require more grooves 8 in
order to allow the optimal flow of the resin 3.

[0084] A higher number of grooves 8 also facilitates the removal of the
object A from the plate 6.

[0085] On the other hand, a reduced number of grooves 8 increases the
surface area of the work surface 7, thus improving the adhesion of the
object A during processing.

[0086] By way of example, it has been found that grooves 8 approximately
one millimetre wide arranged at a mutual distance of about one millimetre
represent a good compromise in many circumstances.

[0087] It is evident, however, that in special cases it will be possible
to use even one groove 8 only.

[0089] In particular, and as shown in FIG. 4, the above mentioned cross
section 11 is rectangular.

[0090] According to a variant embodiment of the plate of the invention,
indicated in FIG. 4a by reference number 6', the cross section 11' has an
area 12 whose width exceeds the width 10 of the same section at the level
of the work surface 7.

[0091] In other words, the cross section 11' features an undercut surface
that, advantageously, facilitates the adhesion of the three-dimensional
object A to the groove 8 during the processing cycle.

[0092] The undercut is small enough not to hinder the removal of the
finished three-dimensional object A from the plate 6.

[0093] Preferably but not necessarily the above mentioned cross section 11
has the shape of a trapezium, with the long base defining the bottom 2a
of the groove 8 and the short base 10 corresponding to the opening of the
groove 8 on the work surface 7.

[0094] According to a further variant embodiment, indicated in FIG. 4b by
reference number 6'', the profile of the cross section 11'' features a
recess 13 on one or both of the edges that delimit the cross section 11''
laterally.

[0095] Advantageously, said recess 13 further improves the adhesion of the
three-dimensional object A to the plate 6 during the processing cycle.
The depth of the above mentioned recess 13 is preferably limited to a few
tenths of a millimetre, in such a way as not to hinder the successive
removal of the object A.

[0096] It is obvious that other variant embodiments may have the
characteristics of the previous two embodiments, combined together.

[0097] The cleaning tool 14 shown in FIG. 5 comprises a supporting body 15
from which one or more mutually parallel elongated elements 16 develop,
each one of which is configured so as to slide inside a corresponding
groove 8 of the plate 6.

[0098] The elongated elements 16 are arranged according to a reference
plane Y and feature mutual distances that are the same as the mutual
distances between the corresponding grooves 8.

[0099] The sliding of the elongated elements 16 inside the corresponding
grooves 8 of the plate 6 makes it possible to exert a thrusting action on
the three-dimensional object A that, advantageously, causes it to be
removed from the work surface 7, as shown in FIGS. 7 and 8.

[0100] Preferably but not necessarily the tool 14 is provided with a
number of elongated elements 16 equal to the number of grooves 8 of the
plate 6, in such a way as to allow the removal of the three-dimensional
object A with one pass only.

[0101] It is evident, however, that the tool 14 can be provided with any
number of elongated elements 16, even lower than the number of grooves 8.

[0102] As shown in FIG. 6, the width 17 of each elongated element 16 with
respect to a direction parallel to the reference plane Y is preferably
uniform and substantially equal to the width of the corresponding groove
8 of the plate 6.

[0103] In this way, advantageously, each elongated element 16 has the
maximum width compatible with the corresponding groove 8, thus allowing
better distribution of the thrusting action on the three-dimensional
object A.

[0104] The thickness 18 of the elongated elements 16 with respect to a
direction orthogonal to the reference plane Y is preferably uniform along
the direction of development of the elongated elements 16.

[0105] Furthermore, the thickness 18 preferably does not exceed the depth
9 of the corresponding groove 8, so as to advantageously make it possible
to comfortably insert the elongated elements 16 between the
three-dimensional object A and the plate 6.

[0106] It is also preferable that the thickness 18 of the elongated
elements 16 be less than the depth 9 of the grooves 8, so as to
facilitate the penetration of the elongated elements 16 even when the
resin 3 solidifies partially inside the grooves 8, as described above.

[0107] According to a variant embodiment of the invention, not illustrated
herein, the elongated elements 16 have increasing cross section from the
end towards the supporting body 15, thus serving as wedges.

[0108] The elongated elements 16 preferably have rounded ends 16a that
advantageously facilitate their insertion in the corresponding grooves 8,
as shown in FIG. 8.

[0109] The elongated elements 16 are preferably made of a flexible
material, in particular a plastic material, with the advantage of
allowing a more gradual force to be exerted on the object A during
removal from the plate 6, so as to reduce the risk of damaging it.

[0110] The elongated elements 16 in plastic material offer a further
advantage lying in that their hardness is lower than the hardness of the
materials commonly employed for the modelling plates, normally aluminium
or other materials with similar hardness.

[0111] The reduced hardness of the elongated elements 16 prevents them
from removing from the surface of the plate 6 some metal particles that
may contaminate the resin 3 during the successive processing cycles, and
also from damaging the plate 6.

[0112] The tool 14 can obviously be entirely made of a plastic material,
with the advantage of reducing costs.

[0113] For this purpose the depth 9 of the grooves 8 should preferably
exceed 0.5 mm, and preferably be in the order of 1 mm, so that the
thickness of the tool 14 is compatible with the use of a plastic
material.

[0114] It is also evident that, in variant embodiments of the invention,
the tool 14 can be made of any material.

[0115] Obviously, the plate 6 and the tool 14 of the invention can be
supplied in a kit intended to be used in a stereolithography machine 1,
which incorporates the advantages of both components.

[0116] In practice, after the construction of the three-dimensional object
A has been completed, it can be comfortably removed from the plate 6
without damaging it, using the cleaning tool 14.

[0117] In particular, the ends 16a of the elongated elements 16 are
inserted in the corresponding grooves 8 of the plate 6 and are then
slided along the grooves 8, as shown in FIG. 7.

[0118] During the sliding operation, the tool 14 is kept slightly
inclined, so as to thrust the three-dimensional object A towards the
outside of the plate 6 until it comes off.

[0119] Advantageously, as the three-dimensional object A is thrusted at
the level of its base, it remains intact during separation from the plate
6, leaving no solid residue of resin 3 stuck in the grooves 8, as shown
in FIG. 8.

[0120] Therefore, advantageously, the modelling plate 6 does not require
further cleaning operations before being used for the production of a new
three-dimensional object.

[0121] The above clearly shows that the modelling plate and the
stereolithography machine of the invention achieve all the set objects.

[0122] In particular, the grooved modelling plate makes it particularly
easy to remove the finished object from the plate itself, especially if
using the tool of the invention.

[0123] The use of the tool of the invention ensures an almost perfect
cleaning of the modelling plate.

[0124] Furthermore, the grooves of the plate facilitate the flow of the
resin during the processing cycle, limiting the stress on the bottom of
the tank and thus making it possible to increase the processing speed.

[0125] In any case, further variants of the invention, even if they are
neither described herein nor illustrated in the drawings, must all be
considered protected by the present patent, provided that they fall
within the scope of the following claims.

[0126] Where technical features mentioned in any claim are followed by
reference signs, those reference sings have been included for the sole
purpose of increasing the intelligibility of the claims and accordingly
such reference signs do not have any limiting effect on the protection of
each element identified by way of example by such reference signs.